Not Applicable.
Not Applicable.
Not Applicable
1. Field of the Invention
The invention relates to a guiding device for a rotatable, circular saw blade of a saw, which saw comprises a bench surface plane and a frame which is movable in a supporting structure of the saw and on which frame a motor for driving the saw blade is mounted, which guiding device is arranged for operational cutting movement of the frame along a circular path between a lower position, wherein the saw blade is located completely under the bench surface plane, and an upper position, wherein a circle segment of the saw blade is located above the bench surface plane, wherein the guiding device comprises an arm the end sections of which are linked to the structure and to the frame.
2. Description of the Related Art
In known saws of this type the frame can also support a motor for operation of the saw blade which may be plate-shaped and extend along a saw blade plane. Furthermore, the frame can be supported by the stand via a rotating device mounted rotatably in the stand, the upper part of which device can have a circular disk which is level with the bench surface, and wherein there is provided a slot through which the saw blade can be passed during raising and lowering by means of the operating mechanism. By turning the rotating device the frame and the saw blade can be rotated about a vertical axis, thus enabling sections to be sawed in a blank which extend at an angle in relation to one another. In addition the saw may include a device whereby the saw blade can be tilted about a horizontal axis which extends in the saw blade plane.
During a rotation of such a saw blade which partly projects up from the bench surface, successive saw blade sections which are located under the bench surface are first moved upwards through the slot, then become horizontal at the point which is located vertically above the centre of the saw blade, and finally downwards through the slot.
If a long blank has to be cleft, i.e. split along its longitudinal direction, the rotating device is set in such a manner that the saw blade plane extends parallel to a support strip which is connected to the stand and extends parallel to the bench plate, and the blank is placed against the support strip. The saw blade is then lifted via the frame in such a manner that the saw blade""s upper section extends at a suitable height over the blank, the frame is secured in relation to the stand by suitable means, and the blank moved towards the saw by those sections of the saw blade segment which are successively moved downwards towards the bench surface during the rotation of the saw blade. The blank is hereby influenced by a force which attempts to press it downwards and the blank thus comes into secure abutment against the bench surface while simultaneously being capable of being pushed towards the saw blade. That section of the saw blade, or more precisely that section of the saw blade segment which at a moment during the rotation faces the blank will hereinafter be described as the front section of the saw blade. Similarly, that section of the saw blade which at the moment faces away from the blank and which is moved upwards, will be described as the rear section of the saw blade. That section of the saw blade which is located substantially at the centre of the saw blade and which at the moment is substantially moved horizontally will be described as the central section of the saw blade.
If the length of the blank is greater than the half chord of the segment of the saw blade which projects up through the slot, before the blank has been completely split, the blank may have two adjacent sections which have been conveyed past the central section, and which are connected via a third, not yet sawn-off section, which is located in front of the front section of the saw segment. Due to an internal tension in the third blank section the two split adjacent sections may be moved towards each other. If the tension is sufficiently great, the saw blade may be clamped between the adjacent sections, with the result that an upwardly directed force is exerted on the blank, which force attempts to fling it up at great speed. If the blank is flung up, it may result in personal injury.
If the two adjacent sections are so long that they extend behind the saw blade before the blank has been completely split, a clamping of the saw blade can be avoided if a plate-shaped splitting element, also called a riving knife, is provided behind the saw blade, this knife being securely fixed to the frame. The riving knife is hereby level with the saw blade, and the riving knife""s plate thickness substantially corresponds to the saw blade""s plate thickness. The riving knife normally extends along and close to the rear periphery of the saw blade up to a level immediately below the saw blade""s uppermost section, i.e. to near the saw blade""s central section. If a riving knife is provided and an attempt is made to move the two adjacent sections of a long blank towards each other, they can cause the riving knife only to be clamped, and not the saw blade, and therefore no attempt is made by the saw blade to move the blank upwards, thus avoiding personal injury.
If the blank has to be cut after splitting, the rotating direction is rotated 90xc2x0, with the result that the saw blade plane extends across the support strip""s longitudinal direction and the riving knife is located on the side of the saw blade which faces away from the support strip. The blank is then placed against the support strip, whereupon the saw blade is raised for sawing the blank. If the width of the blank does not exceed the length of that section of the saw blade which is exposed by the riving knife, viewed from above, when it is raised the saw blade will be able to cut the blank. If this length is exceeded, however, the riving knife will be able to come into abutment against the bottom of the blank, preventing the saw blade from being inserted in the blank and possibly lifting it. Thus the relatively long riving knife severely restricts the potential cutting width for the saw blade. The riving knife, however, should not be removed, since during cutting a clamping of the saw blade may also occur with the risk of personal injury. It is a regrettable fact, however, that many craftsmen remove the riving knife, since it causes too great a reduction in the saw""s capacity.
A saw of the type which is mentioned in the introduction is also known from DK-A-102700 which is considered to represent the closest prior art. This publication shows a guiding device for a rotatable circular saw blade of a saw, which saw comprises a bench shaped stand with a bench surface, the top of which extends in a bench surface plane, and a frame which is moveable in the stand and on which the saw blade is rotatably mounted. The guiding device is arranged for movement of the frame along a circular path between a lower position, wherein the saw blade is located completely under the bench surface plane, and an upper position, wherein a circle segment of the saw blade is located above the bench surface plane. For this purpose the guiding device comprises an arm, the end sections of which are linked to the frame and to the stand. The guiding device also comprises a circular slot in the stand. Another arm, linked to the stand, serves for guiding a riving knife, which knife is also linked to the frame. Thus, the other arm does not serve for guiding the frame.
The object of the invention is to provide a guiding device of the type mentioned in the introduction which permits an increase in the saw""s cutting width, thereby eliminating the above-mentioned disadvantages.
The characteristics of the guiding device according to the invention are presented in the characteristic features stated in the claims.
The invention will now be described in more detail with reference to the drawing which schematically illustrates embodiments of the guiding device according to the invention.